Infer type var tuple contents in more situations

Author: A5rocks

mypy/constraints.py

@@ -136,6 +136,10 @@ def infer_constraints_for_callable(
                 incomplete_star_mapping = True  # type: ignore[unreachable]
                 break
 
+    # some constraints are more likely right than others
+    # so we store them separately and remove unlikely ones later
+    priority_constraints = []
+
     for i, actuals in enumerate(formal_to_actual):
         if isinstance(callee.arg_types[i], UnpackType):
             unpack_type = callee.arg_types[i]
@@ -178,7 +182,7 @@ def infer_constraints_for_callable(
                     )
 
             if isinstance(unpacked_type, TypeVarTupleType):
-                constraints.append(
+                priority_constraints.append(
                     Constraint(
                         unpacked_type,
                         SUPERTYPE_OF,
@@ -273,7 +277,10 @@ def infer_constraints_for_callable(
     if any(isinstance(v, ParamSpecType) for v in callee.variables):
         # As a perf optimization filter imprecise constraints only when we can have them.
         constraints = filter_imprecise_kinds(constraints)
-    return constraints
+    for pconstraint in priority_constraints:
+        constraints = [c for c in constraints if c.type_var != pconstraint.type_var]
+
+    return constraints + priority_constraints
 
 
 def infer_constraints(
@@ -1108,6 +1115,13 @@ def visit_callable_type(self, template: CallableType) -> list[Constraint]:
                 # (with literal '...').
                 if not template.is_ellipsis_args:
                     unpack_present = find_unpack_in_list(template.arg_types)
+
+                    # TODO: do we need some special-casing when unpack is present in actual
+                    # callable but not in template callable?
+                    res.extend(
+                        infer_callable_arguments_constraints(template, cactual, self.direction)
+                    )
+
                     # When both ParamSpec and TypeVarTuple are present, things become messy
                     # quickly. For now, we only allow ParamSpec to "capture" TypeVarTuple,
                     # but not vice versa.
@@ -1125,12 +1139,6 @@ def visit_callable_type(self, template: CallableType) -> list[Constraint]:
                             template_types, actual_types, neg_op(self.direction)
                         )
                         res.extend(unpack_constraints)
-                    else:
-                        # TODO: do we need some special-casing when unpack is present in actual
-                        # callable but not in template callable?
-                        res.extend(
-                            infer_callable_arguments_constraints(template, cactual, self.direction)
-                        )
             else:
                 prefix = param_spec.prefix
                 prefix_len = len(prefix.arg_types)
@@ -1464,6 +1472,7 @@ def repack_callable_args(callable: CallableType, tuple_type: TypeInfo) -> list[T
     list with unpack in the middle, and prefix/suffix on the sides (as they would appear
     in e.g. a TupleType).
     """
+    # TODO: don't repack kw-only args, e.g. with `(a: int, *, b: int)`
     if ARG_STAR not in callable.arg_kinds:
         return callable.arg_types
     star_index = callable.arg_kinds.index(ARG_STAR)

mypy/subtypes.py

@@ -1663,15 +1663,16 @@ def are_parameters_compatible(
 
     trivial_vararg_suffix = False
     if (
-        right.arg_kinds[-1:] == [ARG_STAR]
-        and isinstance(get_proper_type(right.arg_types[-1]), AnyType)
+        right_star is not None
+        and isinstance(get_proper_type(right_star.typ), AnyType)
         and not is_proper_subtype
-        and all(k.is_positional(star=True) for k in left.arg_kinds)
     ):
         # Similar to how (*Any, **Any) is considered a supertype of all callables, we consider
         # (*Any) a supertype of all callables with positional arguments. This is needed in
         # particular because we often refuse to try type inference if actual type is not
         # a subtype of erased template type.
+
+        # This case also ensures that *Any is any length.
         trivial_vararg_suffix = True
 
     # Match up corresponding arguments and check them for compatibility. In

test-data/unit/check-typevar-tuple.test

@@ -2312,18 +2312,18 @@ def good2(*args: str) -> int: ...
 # These are special-cased for *args: Any (as opposite to *args: object)
 def ok1(a: str, b: int, /) -> None: ...
 def ok2(c: bytes, *args: int) -> str: ...
+def ok3(**kwargs: None) -> None: ...
 
 def bad1(*, d: str) -> int: ...
-def bad2(**kwargs: None) -> None: ...
 
 higher_order(good1)
 higher_order(good2)
 
 higher_order(ok1)
 higher_order(ok2)
+higher_order(ok3)
 
 higher_order(bad1)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[NamedArg(str, 'd')], int]"; expected "Callable[[VarArg(Any)], Any]"
-higher_order(bad2)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[KwArg(None)], None]"; expected "Callable[[VarArg(Any)], Any]"
 [builtins fixtures/tuple.pyi]
 
 [case testAliasToCallableWithUnpack2]
@@ -2381,11 +2381,11 @@ def func(x: Array[Unpack[Ts]], *args: Unpack[Ts]) -> Tuple[Unpack[Ts]]:
     ...
 
 def a2(x: Array[int, str]) -> None:
-    reveal_type(func(x, 2, "Hello"))  # N: Revealed type is "Tuple[builtins.int, builtins.str]"
-    reveal_type(func(x, 2))           # E: Cannot infer type argument 1 of "func" \
-                                      # N: Revealed type is "builtins.tuple[Any, ...]"
-    reveal_type(func(x, 2, "Hello", True))   # E: Cannot infer type argument 1 of "func" \
-                                             # N: Revealed type is "builtins.tuple[Any, ...]"
+    reveal_type(func(x, 2, "Hello"))  # N: Revealed type is "Tuple[Literal[2]?, Literal['Hello']?]"
+    reveal_type(func(x, 2))           # N: Revealed type is "Tuple[Literal[2]?]" \
+                                      # E: Argument 1 to "func" has incompatible type "Array[int, str]"; expected "Array[int]"
+    reveal_type(func(x, 2, "Hello", True))   # N: Revealed type is "Tuple[Literal[2]?, Literal['Hello']?, Literal[True]?]" \
+                                             # E: Argument 1 to "func" has incompatible type "Array[int, str]"; expected "Array[int, str, bool]"
 [builtins fixtures/tuple.pyi]
 
 [case testTypeVarTupleTypeApplicationOverload]
@@ -2628,3 +2628,37 @@ def fn(f: Callable[[*tuple[T]], int]) -> Callable[[*tuple[T]], int]: ...
 def test(*args: Unpack[tuple[T]]) -> int: ...
 reveal_type(fn(test))  # N: Revealed type is "def [T] (T`1) -> builtins.int"
 [builtins fixtures/tuple.pyi]
+
+[case testKwargWithTypeVarTupleInference]
+# https://github.com/python/mypy/issues/16522
+from typing import Generic, TypeVar, Protocol
+from typing_extensions import TypeVarTuple, Unpack
+
+PosArgT = TypeVarTuple("PosArgT")
+StatusT = TypeVar("StatusT")
+StatusT_co = TypeVar("StatusT_co", covariant=True)
+StatusT_contra = TypeVar("StatusT_contra", contravariant=True)
+
+class TaskStatus(Generic[StatusT_contra]):
+    def started(self, value: StatusT_contra) -> None: ...
+
+class NurseryStartFunc(Protocol[Unpack[PosArgT], StatusT_co]):
+    def __call__(
+        self,
+        *args: Unpack[PosArgT],
+        task_status: TaskStatus[StatusT_co],
+    ) -> object: ...
+
+def nursery_start(
+    async_fn: NurseryStartFunc[Unpack[PosArgT], StatusT],
+    *args: Unpack[PosArgT],
+) -> StatusT:  ...
+
+def task(a: int, b: str, *, task_status: TaskStatus[str]) -> None: ...
+
+def test() -> None:
+    reveal_type(nursery_start(task, "a", 2))  # N: Revealed type is "builtins.str" \
+                                              # E: Argument 1 to "nursery_start" has incompatible type "Callable[[int, str, NamedArg(TaskStatus[str], 'task_status')], None]"; expected "NurseryStartFunc[str, int, str]" \
+                                              # N: "NurseryStartFunc[str, int, str].__call__" has type "Callable[[str, int, NamedArg(TaskStatus[str], 'task_status')], object]"
+    reveal_type(nursery_start(task, 1, "b"))  # N: Revealed type is "builtins.str"
+[builtins fixtures/tuple.pyi]